As a method for producing a (meth)acrylic polymer, atom transfer radical polymerization (ATRP) has been found which is a living radical polymerization process that uses, for example, a transition metal complex consisting of a transition metal or transition metal compound and a multidentate amine as the polymerization catalyst (see Patent Literatures 1 and 2). However, these patent literatures disclose no means for reducing the amount of the polymerization catalyst to the order of several hundred ppm based on the monomer weight. In the case of using the above-mentioned technique industrially, since the large amount of transition metal or transition metal compound and transition metal complex used as the catalyst, for example, causes discoloration of the polymer, inhibits a reaction for introducing functional groups, or causes a contact fault when used in electrical parts, it is necessary to remove. However, the removal of the transition metal compound requires extremely a large amount of labor and costs (Patent Literatures 3 to 5).
In this context, it has recently been found that the polymerization is allowed to proceed with several tens of ppm of transition metal atoms by activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) (see Patent Literature 6), in which a reducing agent is characteristically used to reduce the amount of highly oxidized transition metal complexes whose accumulation causes retardation or termination of polymerization; or by single electron transfer living radical polymerization (SET LRP) (see Patent Literature 7), in which a transition metal is characteristically allowed to disproportionate in a highly polar solvent.
In addition, the polymerization has also been found to proceed with a concentration of transition metal atoms as dilute as from several tens to several hundred ppm based on monomer by, for example, using a transition metal complex catalyst containing a halogen atom of a higher period in the periodic table than that of a halogen atom at the end of an initiator (see Patent Literature 8); combining two types of multidentate amines (see Patent Literature 9); or adding an amine in excess relative to a metal catalyst (see Patent Literatures 9 and 10).